Muscle dynamics analysis by clustered categories during jogging in patients with anterior cruciate ligament deficiency.

BACKGROUND: Patients with anterior cruciate ligament (ACL) deficiency (ACLD) tend to have altered lower extremity dynamics. Little is known about the changes in dynamic function and activation during jogging in patients with ACLD. METHODS: Twenty patients with an injured ACL before ACL reconstruction (ACLD group) and nine healthy male volunteers (control group) were recruited. Each volunteer repeated the jogging experiment five times. Based on the experimental data measured, a musculoskeletal multibody dynamics model was employed to simulate the tibiofemoral joint dynamics during jogging. Eighteen muscles were used for analysis. The obtained dynamics data were used for clustering and curve difference analysis. RESULTS: The 18 muscles studied were divided into 3 categories. All the quadriceps, the soleus, the gastrocnemius, and the popliteus were classified as label 1. All the hamstrings were classified as label 2, and the sartorius muscles were classified as label 3. Among them, the classification of the short head of the biceps femoris was significantly different between the two groups (P < 0.001). The force curves of all 18 muscles and the between-group differences were studied according to clustered categories. Most muscle force in label 1 was approaching zero in the terminal stance phase, which was significantly lower than that in the control group (P < 0.05). The muscle force in label 2 had areas with significant differences in the stance phase. Muscle force in label 3 was significantly lower than that in the control group in the pre-swing phase. CONCLUSIONS: This study showed that there are various changes of muscle function and activation in patients with ACLD. Through clustering and curve analysis, the joint reactions and changes of different muscle forces in the gait cycle between the ACLD and control groups could be further clarified.

Finite element analysis of stress in oral mucosa and titanium mesh interface.

BACKGROUND: The stiffness of titanium mesh is a double-blade sword to repair larger alveolar ridges defect with excellent space maintenance ability, while invade the surrounding soft tissue and lead to higher mesh exposure rates. Understanding the mechanical of oral mucosa/titanium mesh/bone interface is clinically meaningful. In this study, the above relationship was analyzed by finite elements and verified by setting different keratinized tissue width in oral mucosa. METHODS: Two three-dimensional finite element models were constructed with 5 mm keratinized tissue in labial mucosa (KM cases) and 0 mm keratinized tissue in labial mucosa (LM cases). Each model was composed of titanium mesh, titanium screws, graft materials, bone, teeth and oral mucosa. After that, a vertical (30 N) loadings were applied from both alveolar ridges direction and labial mucosa direction to stimulate the force from masticatory system. The displacements and von Mises stress of each element at the interfaces were analyzed. RESULTS: Little displacements were found for titanium mesh, titanium screws, graft materials, bone and teeth in both LM and KM cases under different loading conditions. The maximum von Mises stress was found around the lingual titanium screw insertion place for those elements in all cases. The keratinized tissue decreased the displacement of oral mucosa, decreased the maximum von Mises stress generated by an alveolar ridges direction load, while increased those stress from labial mucosa direction load. Only the von Mises stress of the KM cases was all lower than the tensile strength of the oral mucosa. CONCLUSION: The mucosa was vulnerable under the increasing stress generated by the force from masticatory system. The adequate buccal keratinized mucosa width are critical factors in reducing the stress beyond the titanium mesh, which might reduce the titanium exposure rate.

Influence of different diameter reductions in the labial neck region on the stress distribution around custom-made root-analogue implants.

This study was designed to investigate the influence of diameter reductions on the stress distribution around root-analogue implants via 3D finite element analysis. Four root-analogue implant models with different diameter reductions (0, 1, 2, or 3 mm), a traditional threaded implant and congruent bone models were created through reverse engineering. A 100-N force was applied parallel with and in a 45° angle to the implant axis, respectively. The stress concentration in the labial neck area around implants with 1-2 mm diameter reduction was lower than seen with no reduction. When the implant diameter was reduced by 3 mm, there were obvious stress concentrations in both implant and bone (the maximum stress was 206  and 111 MPa, respectively). In other groups, the maximum stress was 65.1 MPa in the bone and 108 MPa in the implant. Additionally, the stress concentration in the bone around the root-analogue implant when the implant diameter was reduced by 0-2 mm (maximum stress of 65.1 MPa) was obviously smaller than that around the traditional implant (maximum stress 130.4 MPa). Reducing the diameter of maxillary central incisor root-analogue implants by up to 2 mm next to the labial cortical bone could help disperse stress.

Effect of partial restorative treatment on stress distributions in non-carious cervical lesions: a three-dimensional finite element analysis.

BACKGROUND: Partial restoration combined with periodontal root coverage surgery can be applied to the treatment of non-carious cervical lesions (NCCLs) accompanied with gingival recessions in clinical practice. However, the feasibility of NCCL partial restorative treatment from a biomechanical perspective remains unclear. This study aimed to investigate the effect of partial restorations on stress distributions in the NCCLs of mandibular first premolars via three-dimensional finite element analysis. METHODS: Three-dimensional finite element models of buccal wedge-shaped NCCLs in various locations of a defected zenith (0 mm, 1 mm, and 2 mm) were constructed and divided into three groups (A, B, and C). Three partially restored NCCL models with different locations of the lower restoration border (1 mm, 1.5 mm, and 2 mm), and one completely restored NCCL model were further constructed for each group. The following restorative materials were used in all restoration models: composite resin (CR), glass-ionomer cement (GIC), and mineral trioxide aggregate (MTA). The first principal stress distributions under buccal oblique loads of 100 N were analyzed. Restoration bond failures were also evaluated based on stress distributions at dentin-restoration interfaces. RESULTS: When the partial restoration fully covered the defected zenith, the first principal stress around the zenith decreased and the maximum tensile stress was concentrated at the lower restoration border. When the partial restoration did not cover the defected zenith, the first principal stress distribution patterns were similar to those in unrestored models, with the maximum tensile stress remaining concentrated at the zenith. As the elastic modulus of the restorative material was altered, the stress distributions at the interface were not obviously changed. Restoration bond failures were not observed in CR, but occurred in GIC and MTA in most models. CONCLUSIONS: Partial restorations that fully covered defected zeniths improved the stress distributions in NCCLs, while the stress distributions were unchanged or worsened under other circumstances. CR was the optimal material for partial restorations compared to GIC and MTA.

Finite Element Analysis of Two- and Three-Dimensional Fixation in Treating Mandibular Symphyseal Fracture Combined With Bilateral Condylar Intracapsular Fractures.

ABSTRACT: The aim of this study was to compare through finite element analysis two- and three-dimensional (2D and 3D) fixation in the treatment of mandibular symphyseal fracture combined with bilateral condylar intracapsular fractures. The authors created 2 fixation models for the above fracture, and analyzed the stress and displacement in the mandible and fixation materials under 3 loading conditions. The von Mises stress of the mandible and plates peaked during lateral occlusion, and was lowest during central occlusion. In all conditions, stresses in the fixation materials did not exceed the yield stress of titanium. The inferior border of the symphyseal fracture segments showed opposing displacements, and the mandible tended to widen in the 2D fixation model. However, the fracture displacement did not exceed 150 µm for either fixation method. The results suggested that after well reduction and fixation of condylar intracapsular fractures, either 2D or 3D fixation for symphyseal fracture can provide adequately strong fixation. Compared with 2D fixation, 3D fixation has more advantages in controlling the mandibular width and preventing the fixation materials from enduring excessive stress.

A Finite Element Analysis Model is Suitable for Biomechanical Analysis of Orbital Development.

ABSTRACT: The authors investigated orbital bone development in congenital microphthalmia (CM) using a three-dimensional finite element analysis model, after the orbital dimension deficiency was improved with a self-inflating hydrogel expander implant.Data of a 2-year-old male CM patient were examined. The orbital structure, eyeball, eye muscles, and self-inflating hydrogel expander were constructed according to computed tomography examination data. The effects of self-expanding spherical hydrogel at various locations in the muscle cone on orbital bone development were examined using 3-mL self-expanding expanders placed at shallow (model 1: 2 mm depth) and deep (model 2: 8 mm depth) muscle cone positions. This model simulated the hydrogel expansion process; the orbital bone biomechanics and radial displacement nephograms were obtained when the hydrogel volume increased 3, 5, 7, and 9 times and analyzed.The orbital bone biomechanics were concentrated at the medial orbital wall center, gradually spreading to the whole orbital wall. Biomechanics and radial displacement of the inferior temporal and lateral distal orbital wall region were the most significant, and were more significant in model 1 than in model 2.Finite element analysis is suitable for the biomechanical analysis of orbital development in CM. The shallow position inside CM patients' muscle cone is the optimal site for hydrogel implantation.

Influence of sagittal root positions on the stress distribution around custom-made root-analogue implants: a three-dimensional finite element analysis.

BACKGROUND: Stress concentration may cause bone resorption even lead to the failure of implantation. This study was designed to investigate whether a certain sagittal root position could cause stress concentration around maxillary anterior custom-made root-analogue implants via three-dimensional finite element analysis. METHODS: The von Mises stresses in the bone around implants in different groups were compared by finite element analysis. Six models were constructed and divided into two groups through Geomagic Studio 2012 software. The smooth group included models of unthreaded custom-made implants in Class I, II or III sagittal root positions. The threaded group included models of reverse buttress-threaded implants in the three positions. The von Mises stress distributions and the range of the stresses under vertical and oblique loads of 100 N were analyzed through ANSYS 16.0 software. RESULTS: Stress concentrations around the labial lamella area were more prominent in the Class I position than in the Class II and Class III positions under oblique loading. Under vertical loading, the most obvious stress concentration areas were the labial lamella and palatal apical areas in the Class I and Class III positions, respectively. Stress was relatively distributed in the labial and palatal lamellae in the Class II position. The maximum von Mises stresses in the bone around the custom-made root-analogue implants in this study were lower than around traditional implants reported in the literature. The maximum von Mises stresses in this study were all less than 25 MPa in cortical bone and less than 6 MPa in cancellous bone. Additionally, compared to the smooth group, the threaded group showed lower von Mises stress concentration in the bone around the implants. CONCLUSIONS: The sagittal root position affected the von Mises stress distribution around custom-made root-analogue implants. There was no certain sagittal root position that could cause excessive stress concentration around the custom-made root-analogue implants. Among the three sagittal root positions, the Class II position would be the most appropriate site for custom-made root-analogue implants.

Influence of remaining tooth structure and restorative material type on stress distribution in endodontically treated maxillary premolars: A finite element analysis.

STATEMENT OF PROBLEM: How tooth preparation and material type affect the stress distribution of endodontically treated teeth restored with endocrowns remains unclear. PURPOSE: The purpose of this finite element (FE) study was to determine the influence of the quantity of remaining dental tissues and material type on stress distribution in endodontically treated maxillary premolars using 3-dimensional FE analysis. MATERIAL AND METHODS: Five 3-dimensional FE models were constructed on the basis of the restorative methods used and the quantity of preserved tooth tissues: a sound maxillary premolar, an endodontically treated maxillary premolar restored with composite resin, and endodontically treated maxillary premolars restored with endocrowns with thicknesses of 1.0 mm, 2.0 mm, and 3.0 mm. The following endocrown materials were used: Paradigm MZ100, IPS Empress, IPS e.max CAD, and In-Ceram Zirconia. Stress distributions were analyzed under vertical and oblique loads. RESULTS: As the quantity of preserved dental tissues increased, the von Mises stress in dentin decreased, and the peak von Mises strain value of the cement layer increased. When the elastic modulus of the endocrown material increased, the von Mises stress in endocrown and dentin increased, and the peak von Mises strain value of the cement layer decreased. CONCLUSIONS: Although the conservative preparation of teeth for endocrowns is likely to protect the residual tooth structure, it may cause future cohesive bonding failure. An increase in the elastic modulus of the material may benefit the durability of bonding between the endocrown and the abutment tooth; however, it may cause fracture of the residual tooth structure.

[Finite element analysis of the maxillary central incisor with crown lengthening surgery and post-core restoration in management of crown-root fracture].

OBJECTIVE: To construct the finite element models of maxillary central incisor and the simulations with crown lengthening surgery and post-core restoration in management of different crown-root fracture types, to investigate the stress intensity and distributions of these models mentioned above, and to analyze the indications of crown lengthening from the point of view of mechanics. METHODS: An extracted maxillary central incisor and alveolar bone plaster model were scanned by Micro-CT and dental impression scanner (3shape D700) respectively. Then the 3D finite element models of the maxillary central incisor and 9 simulations with crown lengthening surgery and post-core restoration were constructed by Mimics 10.0, Geomagic studio 9.0 and ANSYS 14.0 software. The oblique static force (100 N) was applied to the palatal surface (the junctional area of the incisal 1/3 and middle 1/3), at 45 degrees to the longitudinal axis, then the von Mises stress of dentin, periodontal ligament, alveolar bone, post and core, as well as the periodontal ligament area, were calculated. RESULTS: A total of 10 high-precision three-dimensional finite element models of maxillary central incisor were established. The von Mises stress of models: post>dentin>alveolar bone>core>periodontal ligament, and the von Mises stress increased linearly with the augmentation of fracture degree (besides the core). The periodontal ligament area of the crown lengthening was reduced by 12% to 33%. The von Mises stress of periodontal ligament of the B2L2c, B2L3c, B3L1c, B3L2c, B3L3c models exceeded their threshold limit value, respectively. CONCLUSION: The maxillary central incisors with the labial fracture greater than three-quarter crown length and the palatal fracture deeper than 1 mm below the alveolar crest are not the ideal indications of the crown lengthening surgery.

[Influence of attachment type on stress distribution of implant-supported removable partial dentures].

OBJECTIVE: To compare influences of different retention attachments on stress among supporting structures. METHODS: By 3-dimensional laser scanner and reverse engineering computer aided design (CAD) software, a basic partially edentulous digital model with mandibular premolar and molar missing was established. Implant attachment and removable partial dentures (RPD) were added into the basic model to build three kinds of models: RPD only, RPD + implant + Locator attachment, and RPD + implant + Magfit attachment. Vertical and inclined loads were put on artificial teeth unilaterally. By means of 3-dimensional finite element analysis, the stress distribution and displacement of the main supportive structures were compared. RESULTS: A complete 3-dimensional finite element model was established, which contained tooth structure, and periodontal structures. The displacement of the denture was smaller in Locator (9.38 µm vertically, 45.48 µm obliquely) and Magfit models (9.54 µm vertically, 39.45 µm obliquely) compared with non-implant RPD model (95.27 µm vertically, 155.70 µm obliquely). Compared with the two different attachments, cortical bone stress value was higher in Locator model (Locator model 10.850 MPa vertically, 43.760 MPa obliquely; Magfit model 7.100 MPa vertically, 19.260 MPa obliquely).The stress value of abutment periodontal ligamentin Magfit model (0.420 MPa vertically) was lower than that in Locator model (0.520 MPa vertically). CONCLUSION: The existence of implant could reduce maximum von Mises value of each supportive structure when Kennedy I partially edentulous mandible was restored. Comparing the structure of Magfit and Locator attachment, the contact of Magfit attachment was rigid, while Locator was resilient. Locator attachment could improve stability of the denture dramatically. Locator had stronger effect on defending horizontal movement of the denture.

Influence of occlusal contact and cusp inclination on the biomechanical character of a maxillary premolar: a finite element analysis.

STATEMENT OF PROBLEM: Restoring teeth with large amounts of dentin loss is challenging, especially for posterior teeth with high cusps. However, strategies for reducing the lateral forces are based on clinical experience instead of than scientific evidence. PURPOSE: The purpose of this study was to analyze the biomechanical characteristics of maxillary premolars with different ferrule configurations and to investigate the influence of occlusal contact and cusp inclination on stress distribution with the finite element method. MATERIAL AND METHODS: Five numerical casts of a maxillary premolar were generated; each adopted 1 of the 5 coronal dentin configurations: i (access cavity with 4-mm dentin height) and ii to v (2-mm complete ferrule, 2-mm facial ferrule, 2-mm palatal ferrule, 2-mm proximal ferrule, and restored with a post and core, respectively). Both gold-alloy and glass-fiber posts were modeled. An oblique load of 200 N was applied to the top, middle, and bottom of the 45-degree facial cusps. The cusp inclination was remodeled to 60 degrees, followed by the application of a 200-N load to the top. The values of the maximum principal stress and von Mises stress were calculated to assess overload risk. RESULTS: When the top of 45-degree facial cusps was loaded, the maximum local stress concentration on dentin was found in teeth with a facial ferrule and restored with a gold-alloy post. When the middle of 45-degree facial cusps were loaded, the principal stresses of teeth with a complete ferrule, palatal ferrule, and proximal ferrule were similar to those of the access cavity teeth. In contrast, the principal stress of a tooth with a facial ferrule was close to that of the access cavity tooth after remodeling the facial inclination to 60 degrees. CONCLUSIONS: Maxillary premolars with only facial dentin remaining show higher local stress on root dentin. Altering the loading position and reducing the facial cusp inclination can reduce local stresses.

Cost function criteria using muscle synergies: Exploring the potential of muscle synergy hypothesis.

BACKGROUND AND OBJECTIVE: Solving the redundant optimization problem for human muscles depends on the cost function. Choosing the appropriate cost function helps to address a specific problem. Muscle synergies are currently limited to those obtained by electromyography. Furthermore, debate continues regarding whether muscle synergy is derived or real. This study proposes new cost functions based on the muscle synergy hypothesis for solving the optimal muscle force output problem through musculoskeletal modeling. METHODS: We propose two new computational cost functions involving muscle synergies, which are extracted from muscle activations predicted by musculoskeletal modelling rather than electromyography. In this study, we constructed a musculoskeletal model for simulation using the "Grand Challenge Competition to Predict In Vivo Knee Loads" dataset. Muscle synergies were obtained using non-negative matrix factorization. Two cost functions with muscle synergies were constructed by integrating the polynomial and min/max criterion. Two new functions were verified and validated in normal, smooth, and bouncy gaits. RESULTS: The muscle synergies based on normal gaits were classified into four modules. The cosine similarities of the first three modules were all >0.9. In the normal and smooth gaits, the forces in most muscles predicted using the two new functions were within three standard deviations of the root mean square error for electromyographic comparisons. Predicted muscle force curves using the four methods as well as characteristic points (i.e., time points in the gait cycle when the significant difference was observed between normal and bouncy gaits) were obtained to validate their predictive capabilities. CONCLUSIONS: This study constructed two new cost functions involving muscle synergies, verified and validated the ability, and explored the potential of muscle synergy hypothesis.

[Analysis of human mandible and temporomandibular joint using three-dimensional finite element method under different mechanical models].

OBJECTIVE: Analysis the result of human mandible and temporomandibular joint using two different three-dimensional finite element method under different mechanical models. METHODS: The 3-dimensional model including cortical and cancellous bone for human mandible was obtained through computed tomography (CT) scan. Then the model was meshed in the software ICEM CFD. The passive and active muscle-force loadings were separately applied on the FE model to simulate the anterior clenching. Stress distributions in two models were compared. RESULTS: The stress distributions of two models were apparently different. In the passive muscle-force model, high stress was mainly distributed in mandibular angle, retromolar trigone, notch and bite point on crown. In the active muscle-force model, high stress was mainly distributed in condylar vertex and neck, mandibular angle, retromolar trigone and bite point on crown. There were some similarities between passive and active muscle loadings. However, large difference existed in condylar region due to the vertices reaction force disparity. CONCLUSION: Closer to actual stressing state of human mandible and temporomandibular joint, the active muscle-force model is a proper biomechanical model for human mandible under anterior clenching.

Leveraging Multivariable Linear Regression Analysis to Identify Patients with Anterior Cruciate Ligament Deficiency Using a Composite Index of the Knee Flexion and Muscle Force.

Patients with anterior cruciate ligament (ACL) deficiency (ACLD) tend to have altered lower extremity kinematics and dynamics. Clinical diagnosis of ACLD requires more objective and convenient evaluation criteria. Twenty-five patients with ACLD before ACL reconstruction and nine healthy volunteers were recruited. Five experimental jogging data sets of each participant were collected and calculated using a musculoskeletal model. The resulting knee flexion and muscle force data were analyzed using a t-test for characteristic points, which were the time points in the gait cycle when the most significant difference between the two groups was observed. The data of the characteristic points were processed with principal component analysis to generate a composite index for multivariable linear regression. The accuracy rate of the regression model in diagnosing patients with ACLD was 81.4%. This study demonstrates that the multivariable linear regression model and composite index can be used to diagnose patients with ACLD. The composite index and characteristic points can be clinically objective and can be used to extract effective information quickly and conveniently.

An Analysis of Trabecular Bone Structure Based on Principal Stress Trajectory.

To understand the mechanism of Wolff's law, a finite element analysis was performed for a human proximal femur, and the principal stress trajectories of the femur were extracted using the principal stress visualization method. The mechanism of Wolff's law was evaluated theoretically based on the distribution of the principal stress trajectories. Due to the dynamics of the loads, there was no one-to-one correspondence between the stress trajectories of the fixed load and the trabeculae in the cancellous architecture of the real bone. The trabeculae in the cancellous bone were influenced by the magnitude of the principal stress trajectory. Equivalent principal stress trajectories suitable for different load changes were proposed through the change in load cycle and compared with the anatomical structure of the femur. In addition, the three-dimensional distribution of the femoral principal stress trajectory was established, and the adaptability potential of each load was discussed. The principal stress visualization method could also be applied to bionic structure design.

Orthodontic craniofacial pattern diagnosis: cephalometric geometry and machine learning.

Efficient and reliable diagnosis of craniofacial patterns is critical to orthodontic treatment. Although machine learning (ML) is time-saving and high-precision, prior knowledge should validate its reliability. This study proposed a craniofacial ML diagnostic workflow base on a cephalometric geometric model through clinical verification. A cephalometric geometric model was established to determine the landmark location by analyzing 408 X-ray lateral cephalograms. Through geometric information and feature engineering, nine supervised ML algorithms were conducted for sagittal and vertical skeleton patterns. After dimension reduction, plane decision boundary and landmark contribution contours were depicted to demonstrate the diagnostic consistency and the consistency with clinical norms. As a result, multi-layer perceptron achieved 97.56% accuracy for sagittal, while linear support vector machine reached 90.24% for the vertical. Sagittal diagnoses showed average superiority (91.60 ± 5.43)% over the vertical (82.25 ± 6.37)%, where discriminative algorithms exhibited more steady performance (93.20 ± 3.29)% than the generative (85.98 ± 9.48)%. Further, the Kruskal-Wallis H test was carried out to explore statistical differences in diagnoses. Though sagittal patterns had no statistical difference in diagnostic accuracy, the vertical showed significance. All aspects of the tests indicated that the proposed craniofacial ML workflow was highly consistent with clinical norms and could supplement practical diagnosis.

Effect of remaining pericervical dentin on biomechanical behavior of endocrown-restored molars with different materials: Three-dimensional finite element and Weibull analyses.

To evaluate the effect of remaining pericervical dentin (PCD) on the biomechanical behavior of endocrown-restored molars with different materials, six three-dimensional finite element (FE) models were reconstructed with different thicknesses and heights of pulp-chamber lateral dentinal wall (PCLDW). IPS Empress 2, In-Ceram Zirconia, and Lava Ultimate were selected as the materials. Compared with the Lava Ultimate FE models, the maximum tensile stress in the FE models using ceramics was higher in the endocrown and lower in the PCD surrounding it, and the overall failure probabilities with different PCLDW thicknesses and heights were similar, ranging from 9.8% to 12.9% under the normal lateral masticatory force, which were lower than the FE models using Lava Ultimate (ranging from 13.4% to 15.1%). Considering the bonding properties of ceramics, endocrown-restored molars using etchable lithium disilicate-reinforced glass ceramic exhibit superior longevity due to the stress shielding effect, regardless of the thickness and height of PCLDW.

Finite element analysis on pushing the molar backwards using invisible aligner with different migration displacement.

PURPOSE: This paper examines the biomechanical mechanism behind the effect of the invisible aligner technique on tooth movement processes. METHODS: To compare the effects of different target positions on tooth movement and the periodontal ligament (PDL), two kinds of aligners were designed to provide displacements of 0.2 mm (Model A) and 0.3 mm (Model B). Different displacements of the maxillary second molar were simulated using the finite element (FE) method. RESULTS: The results of numerical simulations showed that the maximum stress was in the PDL of the distal surface and the palatal surface. The stress of the PDL in Model B was larger than Model A, with the displacement of the second molar 0.027 mm in Model A, by 44.9% lesser than that in Model B. CONCLUSIONS: The aligner that provided a displacement of 0.2 mm was more suitable for pushing the second molar backward in the initial stage. During the tooth movement processes, the displacement of the crown was larger than that of the root and the displacement decreased gradually from the crown to the root. In addition, the displacement and rotation of teeth during orthodontic treatment were measured and analysed.

Relationship between high intra-abdominal pressure and compliance of the pelvic floor support system in women without pelvic organ prolapse: A finite element analysis.

Previous studies mainly focused on the relationship between the size of the prolapse and injury to the supporting tissues, but the strain and stress distributions of the supporting tissues as well as high-risk areas of injury are still unknown. To further investigate the effect of supporting tissues on organs and the interactions between organs, this study focused on the relationship between high intra-abdominal pressure and the compliance of the pelvic floor support system in a normal woman without pelvic organ prolapse (POP), using a finite element model of the whole pelvic support system. A healthy female volunteer (55 years old) was scanned using magnetic resonance imaging (MRI) during rest and Valsalva maneuver. According to the pelvic structure contours traced by a gynecologist and anatomic details measured from dynamic MRI, a finite element model of the whole pelvic support system was established, including the uterus, vagina with cavity, cardinal and uterosacral ligaments, levator ani muscle, rectum, bladder, perineal body, pelvis, and obturator internus and coccygeal muscles. This model was imported into ANSYS software, and an implicit iterative method was employed to simulate the biomechanical response with increasing intra-abdominal pressure. Stress and strain distributions of the vaginal wall showed that the posterior wall was more stable than the anterior wall under high intra-abdominal pressure. Displacement at the top of the vagina was larger than that at the bottom, especially in the anterior-posterior direction. These results imply potential injury areas with high intra-abdominal pressure in non-prolapsed women, and provide insight into clinical managements for the prevention and surgical repair plans of POP.

Three-dimensional radiological anatomy of condyle trabecular bone based on a Volume-of-Interest analysis.

OBJECTIVES: Three-dimensional radiological anatomic characteristics of condyle trabeculae was obtained quantitatively based on a volume-of-interest (VOI) analysis. METHODS: Nine human mandibular condyle specimens were scanned by micro-computed tomography (micro-CT). A total of 34 VOIs were selected from each condyle specimen, which were divided into six layers and four parts to analyze the morphological characteristics of trabeculae based on cylindrical VOIs with a diameter and height of 2 mm. One-way analysis of variance was used to compare the regional differences of morphological parameters among each layer and part. RESULTS: Values for bone mineral density, bone volume/total volume, trabecular thickness, and trabecular bone number were greater in the anterior part compared with the posterior part; and the lateral part was larger than the medial part in the first, second, and third layers, while the medial part was larger in the fourth and fifth layers; these values in the first and sixth layers were much larger, while those in the third and fourth layers were smaller. Bone surface area/bone volume, trabecular spacing, and trabecular bone pattern factor were larger in the posterior part than in the anterior part; and the lateral part was larger than the medial part in the fourth and fifth layers, while the medial part was larger in the first and second layers. CONCLUSIONS: The morphological distribution of VOIs was anisotropic within trabecular bone of human mandibular condyles. The upper and lower ends of trabecular bone were much more compact, with higher bone density, trabecular thickness, and trabecular number than in the middle layers.